ammonium sulfate 0.17 M - polyethylene glycol 4000 25.5% (w/v) - glycerol 15% solution
How can I calculate the amount required to prepare the following buffer?
I want to prepare 1000 microliter
(NH4)2SO4 MW=132.14 g/mol
1M --> 132.14 g --> 1 L (1000 ml)
--> 0.13214 g --> 1 ml (1000 microL)
0.17M --> x = (0.17 x 0.13214)/1= 0.02246 g = 22.46 microg
PEG4000 25.5% (w/v) --> 255 microg
glycerol 15% --> 150 microL
I would definitely recommend making a larger solution and then using what you need. As you would need an extremely accurate balance to measure the ammonium sulfate properly.
Initial Volume = (Final Concentration / Initial Concentration) * Final Volume
Units of Concentration must be the same. You pick the final volume.
Stock Glycerol is 100% glycerol. But you can't actually pipette 100% glycerol. It is too viscous. You have to dilute 100% glycerol to something like 50% glycerol by combining equal parts of 100% glycerol and water in a graduated cylinder.
Stock PEG-4000 is probably sold as 50% (w/v) PEG-4000
To make a concentrated stock solution like 1 M :
grams chemical to dissolve = (Desired Molarity) * (Molecular Weight) * (1 L / 1000 mL) * (Desired volume in mL)
If you are using this stuff for crystallography, Ammonium sulfate crystallizes a lot of proteins but not every protein. Glycerol inhibits the formation of protein crystals in general. Maybe PEG-4000 isn't the correct molecular weight of PEG. Maybe you need PEG-3350, PEG-1000, PEG-20,000, hexylene glycol. Maybe the concentration of all components isn't right. Maybe the pH isn't right. That means you need a buffer. If the buffer pH you want is 6, then Tris-HCl will not work because the pKa is out of range. Pick a different buffer.
So you will be doing a lot of calculations.
I would recommend creating stronger stock solutions for each from which you would calculate the amount you need to create the final solution.
For example: make 2M of Ammonium Sulfate, 50% Glycerol(easier to handle than 100%), and 50% Peg4k.
If required, calculate the stocks with g=Mw * C * V (grams= Molecular Weight x Concentration x Volume)
I would recommend filtering the stocks with 0.45µm or 0.22µm filter before use, if possible.
Note that when making PEG stock solution, you need to add the PEG powder slowly. Start with 1/3rd of your final volume, for during the adding of PEG the volume will increase.
Then from the stocks, use simply C1V1=C2V2 to dilute them down to desired concentration in your final solution.
Fill the volume with dH2O.
Hope this helps.
- Badges
- Science method